1. Field of the invention:
The present invention relates to an actuating mechanism for a gear transmission for automobiles.
2. Description of the Prior Art:
Automobiles such as trucks have conventionally employed a gear transmission mechanism composed of main transmission gearing having multiple ratios and auxiliary transmission gearing having high and low speed ratios. Such gear transmission mechanism is advantageous in that the auxiliary transmission gearing enables the gear transmission mechanism to provide speed ratios twice those of the main transmission gearing, and the gear transmission mechanism is small and lightweight as a whole as compared with the speed ratios available.
FIG. 1 of the accompanying drawings illustrates a conventional speed ratio pattern of such a gear transmission mechanism. Designated at L and H are speed-reduction and direct-drive gear positions in the auxiliary transmission gearing, R1 and R2 first and second reverse gear positions, F1, F2, F3, F4, F5, and F6 first through six forward gear positions.
The conventional speed ratio pattern shown in FIG. 1 is therefore composed of a lefthand pattern A and a righthand pattern B.
When a gear shift is to be effected while the automobile is running up a sloping road, the gear shift has be completed quickly, or it cannot be done as the speed of the automobile is rapidly reduced.
Such a condition will be described with reference to the speed ratio pattern of FIG. 1.
When the third speed ratio is to be reached while the automobile is running at the fourth-speed ratio F4, it is necessary to move a shift lever from the gear position F4 in the pattern B through the gear positions H and L to the gear position F3 in the pattern A. Thus, the path that the shift lever has to follow is quite complex, and it is difficult to follow that path in a short time. The difficulty arises out of the speed ratio pattern, which results from an arrangement shown in FIG. 2.
In FIG. 2, a shaft 10 actuates a shift fork in the auxiliary transmission gearing, and shafts 11, 12 actuate respective shift forks in the main transmission gearing. A shift lever engages teeth 10a, 11a, 11b, 12a, and 12b.
Operation of the arrangement of FIG. 2 is as follows:
When the shift lever engages the tooth 10a to position the shaft 10 as illustrated, the gear position H is reached, that is, the gears in the auxiliary transmission gearing is set to the high speed ratio. When the shift lever is slid from this position in a selecting direction into engagement with the tooth 11a and then shifted to move the shaft 11 in its axial direction, the gear position R2 or F2 is selected.
When the shift lever is moved from the tooth 11a to the tooth 12a and then shifted to move the shaft 12 in its axial direction, the gear position F4 or F6 is selected.
For a transfer from the pattern B to the pattern A, the shift lever is shifted back to the tooth 10a and shifted to move the tooth 10a to a position indicated by 10b, whereupon the gear position L (FIG. 1) is reached, that is, the auxiliary transmission gearing is set to the low speed ratio.
When the shaft 11 or 12 is to be actuated from this position, the shift lever is slid to the tooth 11b or 12b and then shifted to move the tooth 11b or 12b, thus actuating the shaft 11 or 12 in its axial direction. The actuation of the shaft 11 or 12 results in the selection of the gear position R1 or F1 or the gear position F3 or F5 in the pattern A of FIG. 1.
It will be understood therefore that the pattern shown in FIG. 1 arises out of the fact that the shaft 10 in the auxiliary transmission gearing is provided independently of the shaft 11 or 12 in the main transmission gearing.